Individual differ from one another in the way they process information. For some people, separate auditory messages to the two ears merge into a single message; for other people the messages do not fuse. Some people exhibit greater difficulty in gating an irrelevant dimension while processing a relevant one than do other people. This proposal explores the relationships of individual differences among different types of tasks to determine more specifically how people differ in their information processing. For some people does memory retrieval require attention while for others it does not? Or is memory retrieval uniformly non-attentive with individuals differing either in the specificity of memory retrieval or in response biases? Increases in arousal appear to affect attention in similar ways: Under increased arousal, attention is more focussed so that irrelevant information is less interfering. Again what is the exact nature of the changes and how do they interact with individual differences? A variety of reaction-time tasks will be used to answer these questions and noise will be used to manipulate arousal.